Faust from Legend of Dragoon [i didn't use the elemental armours and i was poor as hell back then when i faced him] took me well over 100 tries with the gear i had on me

I found most bosses from LoD somewhat difficult because you had to depend on defend to heal and... well, fights were freaking long!

Heck yeah! That dude's a pain to fight!
I think I had the Red Dr Armor and the Legend Casque for Dart and that was it. I believe I used some items and attacks to kill him.

Actually, some bosses are easier if you just don't transform and if you can do your additions right. I believe that some additions hit more then your dragoon attacks.
I believe the last time I played it, I didn't transform for probably 3/4 of the time, if not more, for boss fights or regular fights.

Yiazmat from FFXII, due to the amount of time it takes to beat this bastard. You'll be spending atleast an hour or two on this guy if you know how to beat him, and the fact that he caps dmg at less than 50% health... and ontop of that, it's possible for him to COMPLETELY REGAIN HIS HEALTH BAR... *suicide*